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Hmm 24.0/24.5 doesn't seem too bad. I didn't think the stock 17's would be much lighter. I have 96's as well and was thinking of going to some 18" CSLs. The 255's will be heavier than the 225 for sure though.

It varies so much between brands and models, and usually the difference is pretty big too. Like, the 225/45-17 General UHP's my car came with are around 21lbs each while my 235/40-18 Michelin Pilot Sports are a full 3 lbs heavier in terms of listed weights. Weights of the wheels on the scales seem to agree with this. So even though I got lighter forged wheels that were an inch bigger in dimeter, I lost almost all of the weight advantage with the new tires.

I guess we are in the same boat. Got my V710 in 18 for a month.
Gas miles from 25-28avg down to 22-23 avg. Wont go over 26mpg on road tirp that I always avg 28-29mpg. Car feels powerless, brake seems doesnt stop the car at all, where with my old stock 17 my brake can grip and stop on dime.

It does look make my car look alot better.

It's interesting you've seen such a dramatic change in gas mileage. I have big, heavy rim, 19" HM2s and I still get 29mpg on the highway. Does the horsepower of a 330 over a 325 make that much difference?

It's interesting you've seen such a dramatic change in gas mileage. I have big, heavy rim, 19" HM2s and I still get 29mpg on the highway. Does the horsepower of a 330 over a 325 make that much difference?

I have, for American purposes, a small engine in my 323ci, and am rolling on 19"s, but I have no complaints, can still easily reach 200km/hr, and am faster off the line than most...if I wanted serious hp numbers, I'd have gone with an M3.

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When determining the effects of wheels on your car's acceleration, you cannot look at weight alone. The more important factor if the "mass moment of inertia" of the wheel/tire setup. By going with larger wheels, you are moving some mass farther away from the point of rotation. Think of an ice skater doing that spin move (whatever it's called, I'm not ghey). As they bring their arms in toward thier body, the speed up because their mass moment of inertia decreases. Larger wheels have the effect of the skater extending their arms out, thereby slowing down their rotation.

If the difference was proportional to the diameter, then you wouldn't see a difference in rolling speed because the larger circumference would make up for the decrease in angular rotation. But that's not case. The mass moment of inertia is proportional to the SQUARE of the diameter. The result is slower acceleration from a larger wheel even if the weight of the wheels being compared are the same.

(mass moment of intertia)=((mass)*(diameter)^2)/8

Tires have the same effect, although you have to consider the inner diameter as well. If you also increase tire width then you are increasing the weight of the tire as well as the diameter, thereby putting the double whammy on your mass moment of inertia.

V710's is my first pick for upgrade wheels but I've been holding it off for a while. Does anyone knows what's the weigh for the ZHP wheel and the Hamann 18x8.5 PG2's I've been using aftermarket wheels since I bought the car so I haven't track the gas mileage

My ZHP wheels front weight 24.7 and the rear 26.2 so the V710's is not that bad consider aftermarket wheels. Also we need to take into count the weight of the tires you choose.

Quote:

Originally Posted by ZZen330

Hmm 24.0/24.5 doesn't seem too bad. I didn't think the stock 17's would be much lighter. I have 96's as well and was thinking of going to some 18" CSLs. The 255's will be heavier than the 225 for sure though.

according to what I've found, my stock Style 44's are 23 lbs and my (on order) 19" Linea Corse wheels are 23.5 lbs so I hope I don't notice that much of a difference...

Real world example; I think style 44s are 17", right? In order to get the same acceleration (and braking) out of 19" wheels, they would need to be approximately 18.4 lbs. I can only give approximate numbers because it really depends on the specific wheel and how it's weight is distributed. The equations I posted earlier assume uniform density from the hub to the rim, which is NEVER the case. If you could magically remove all the spokes and compared 1" thick doughnuts for rims, then the 19s would have to be 20.4 lbs to be comparable to the 23 lb 17s.